Blood pressure and pulse indicator



0a. 20, 1970 J. c. LESHER ET AL 3,535,067

BLOOD PRESSURE AND PULSE INDICATOR Filed March 7. 1967 2 Sheets-Sheet lINVENTORS JOH/V 6.. LESHER ORLO O. NORTON MEX 16% ATTORNEYS Oct. 20,1970 s R ETAL 3,535,067

BLOOD PRESSURE AND PULSE INDICATOR I Filed March 7, 1967 2 Sheets-Sheet2 PHONE EXCHANGE PHONE SUB PHONE UTILITY COMPUTER AMPLIFIER AND ENCODEROFFICE //v VENTORS JOHN 6. LE SHE R ORLO 6'. NOR TON ATTORNEYSTRANSDUCER United States Patent Oflice Patented Get. 20, 1970 3,535,067BLOOD PRESSURE AND PULSE INDICATOR John C. Lesher and Orlo C. Norton,Erie, Pa., assignors to Electro-O-Mech, Inc., Erie, Pa., a corporationof Pennsylvania Filed Mar. 7, 1967, Ser. No. 621,286 In. Cl. A6111 5/02US. Cl. 1282.05 Claims ABSTRACT OF THE DISCLOSURE An indicator forcontinuous monitoring of blood pressure and pulse rate is disclosed, thedevice being continuously worn by a patient and responsive tocirculatory system pulsations. A hydraulic transducer includes areservoir of fluid, the reservoir having a flexible diaphragm which maybe placed in contact with the skin of the patient over the artery to bemeasured. Motion of the diaphragm due to pulsations in the artery actsas a pump to build up pressure in an expansible chamber assembly througha one-way valve arrangement, expansion of the chamber actuating anindicator. A return flow is provided from the fluid chamber to thereservoir through a bleeder valve orifice which is smaller than the feedinto the chamber, the bleeder thus acting as a relief valve to permit asteady indication of pressure. The bleeder permits the meter to returntoward zero on release of applied pressure, and by modifying the size ofthis orifice, the release can permit the return swing of the indicatorto give an approximate reading of pulse rate. The indicator may beremotely located, with the output of the expansible chamber beingconverted to corresponding electric signals for transmission to theremote location.

The present invention relates in general to blood pressure and pulserate indicators and, more particularly, to a simple, compact,light-weight, portable device for accurately measuring blood pressureand indicating pulse rate of a human or an animal.

Prior devices for the measurement of blood pressure or pulse rate havebeen relatively complex devices requiring a skilled operator to obtainthe necessary measurements. For example, the usual blood pressuredetector requires that a pressure sleeve be Wrapped around the arm ofthe person whose blood pressure is being measured, the pressure sleevebeing pumped up by an attendant and slowly released while listening forthe pulse I I I r sound. Such conventional dev1ces, while useful forspecific purposes, are not simple to operate and are neither lightweightnor portable in the sense which the present device is light-weight andportable. The prior devices are not designed to be carried around in anoperable position by the user to permit continuous monitoring ofpressure and pulse rate, and thus are not useful for this purpose. Theconventional method of measuring pulse rate requires that the number ofbeats per unit time be counted; thus the prior art does not provide ameans for obtaining a quick and accurate reading from a device thatcontinuously monitors the patients heart rate.

The present device overcomes the disadvantages of prior devices byproviding a simple, light-weight and portable instrument that can becontinuously Worn by a patient for use in monitoring and for measuringeither pulse rate or blood pressure, or both. In a preferred form, thedevice is incorporated in a housing similar in size to a wrist watch,permitting the device to be worn on the wrist where it is adapted tosense the pressure and pulse rate in the arteries found there. Thesubject device is highly portable by reason of its size and mode ofoperation, giving a convenient and continuous indication that may beeasily read by the patient or by an attendant, and which does notrequire a time-consuming set-up procedure for obtaining pressurereadings. When adapted for pulse rate measurements, the device willindicate such readings at a glance.

It is therefor an object of the present invention to provide a simple,light-weight and portable indicator for blood pressure and for pulserate.

Another object of the present invention is the provision of a portableindicator device which responds to pulsations of a patients heart togive a continuous reading of blood pressure and which may, with the aidof an assistant, be used to obtain readings of diastolic and systolicpressures.

A further object of the present invention is the provision of a portableindicator which responds to arterial or heart motion to give a pulserate indication.

An additional object of the present invention is to provide a portableindicator which may be worn by a patient as a wrist watch is worn, thedevice being easily adaptable to provide high or low pressuremeasurements or, with less accuracy, both pressure and pulse ratemeasurements at the same time, the device being secured in place withsufiicient tension to permit response to arterial pulsations.

Another object of the present invention is the provision of alightweight measuring device which can be left on a patient unattended,the device measuring pulse rate and/or blood pressure and being capableof producing an electrical output corresponding to these measurementswhich can be transmitted to a remote location for continuous monitoring.

Briefly, the present device comprises a hydraulic transducer whichtransfers the pulsating motion from an artery or vein to an indicatingmeter. This is accomplished by means of a reservoir of fluid, thereservoir having a flexible diaphragm which is in contact with the skinof the patient over the artery to be measured. The motion of thediaphragm due to pulsations in the artery acts as a pump to build uppressure in an expansible chamber assembly, or hydraulic cylinder,through a one-way valve arrangement. The expansion of the cylinder inresponse to fluid pressure transferred from the resevoir mechanicallydrives an indicating meter through a gear mechanism. A return flow lineis provided from the fluid chamber of the hydraulic cylinder to thereservoir, the return line being fed through a valve orifice which issmaller than the opening of the feed line into the chamber. The smallorifice acts as a relief valve to allow a steady indication of pressureon the meter and to permit the meter to return toward zero on release ofthe applied pressure. By modifying the size of this orifice, the releaseof pressure from the hydraulic chamber can be made sufficiently fast topermit the return swing of the meter indicator to give an approximatereading of pulse rate. An alternative to this hydraulic system is theprovision of a strain gauge device to respond to the motion of theexpansible chamber assembly to produce a varying electrical output thatcan be transmitted over transmission lines, such as conventionaltelephone cables to a doctors office, where the rate and amplitude ofthe pulses could be monitored.

The foregoing objects and features of the invention as well as variousadditional advantages and modifications will become more apparent tothose skilled in the art from what follows. Although the characteristicfeatures of the invention are set forth with particularity in theappended claims, the invention will be understood more clearly and fullyfrom the following detailed description taken in connection with theaccompanying drawings in which:

FIG. 1 is a perspective view of a form of the indicator device adaptedto be worn on the wrist;

FIG. 2 is a diagrammatic illustration of the hydraulic and mechanicalarrangements by means of which readings are obtained;

FIG. 3 is a modification of the device of FIG. 2; and

FIG. 4 is a diagrammatic illustration of a further modification of thedevice as it may be applied to a remote indicating device.

Referring now to the illustration of FIG. 1, there is shown a bloodpressure indicator constructed in accordance with the present invention,wherein the indicator is adapted to be worn on the wrist in the mannerof a wrist watch. The indicator device includes a movable needlepivotally mounted at the center of an indicator face 12 mounted in awatch-like housing 14. The indicator face includes calibrated scales 16for providing the desired readings while the housing 14 is held in placeby an arm band 18. Although the device is here illustrated in the formof a wrist-carried indicator, it will be apparent that the mechanismdescribed herein can be incorporated in any number of ways into varioushousings for measuring pressure and pulse at any convenient spot on thebody. The arm band 18, or equivalent means for holding the indicator inplace, preferrably is adjustable to permit the device to be held againstan artery, the pulsations of which are to be measured, with sufficientfirmness to insure an accurate reading. Normally, the arm band will betightened to the point where the indicator needle 10 will give apredetermined reading so that all measurements will be made from thesame pressure starting point.

Referring now to the diagrammatic illustration of FIG. 2, the indicatorneedle 10 is illustrated as being mounted for rotation on a pivot axis20. A hair spring arrangement 22. is connected between a fixed point inthe housing and needle 10 to urge the needle toward a rest position asdetermined by the needle stop peg 24. A small gear 26 is fixed to needle10 for rotation therewith, the gear being driven by a curved rackelement 28 which is driven against the stop peg 24 by hair spring 22when the system is at rest. Rack 28 is carried by a lever arm 30 mountedfor rotation about a pivot axis 32 suitably mounted in housing 14. Incontact with lever arm 30 some distance from the pivot axis 32 is anexpansible chamber assembly, or hydraulic cylinder, 34 having a piston36 adapted for motion within its housing 38. Hydraulic fluid underpressure is fed to the fluid chamber of the hydraulic cylinder 34 by wayof a feed line 40, the fluid pressure in line causing the piston 36 tomove out of housing 38 and against the lever arm 30. As is well known inthe hydraulic art, the motion of piston 36 will be proportional to thepressure in feed line 40; thus, the rotation of lever arm about itspivot axis 32 will also be proportional to the fluid pressure to causeindicator needle 10 to rotate about its pivot axis 20 by a similarlyproportional amount. A feedback or bleeder tube 42 is connected to thefluid chamber in hydraulic cylinder 34 through a very small orificevalve 44. The orifice 44 is sufficiently small as not to appreciablyaffect the build up of pressure in the fluid chamber of cylinder 34,While being sufficiently large to permit fluid in the chamber to bereleased shortly after reduction of the pressure being applied to thesystem.

Supplying the hydraulic pressure to feed line 40 is a fluid reservoir 46having a flexible diaphragm 48 attached in sealing relationship to acasing 50. Casing 50 is, in the preferred embodiment, a portion ofindicator housing 14. The positioning of the reservoir and flexiblediaphragm is such that the diaphragm will be placed over an artery orvein 52 when the indicator device is being worn by a patient. Expansionand contraction of artery 52 forces fluid from reservoir 46 throughone-way valve opening 54 into the valve housing 56 and thence through asecond valve opening 58 into the valve chamber 60. Valve openings 54 and56 are of sufficient size to permit free flow of the hydraulic fluidfrom the reservoir through valve chamber 60 to the feed line 40 which isconnected by suitable means to the valve chamber. In order to insure aone-way flow of hydraulic fluid through the feed line 40,

whereby pressure may build up in the hydraulic cylinder assembly 34, aspring-loaded valve clapper 62 is arranged to cover valve opening 54.The clapper is held in place by a coil spring 64 so that opening 54 isnormally covered. The resilience of spring 64 is so adjusted that evenslight pressure from artery 52 will permit fluid to flow from reservoir46 through opening 54 to chamber 60 while insuring that clapper 62 willclose upon release of such pressure. Bleeder tube 42, is connected toreservoir 46 to return hydraulic fluid from assembly 34 to thereservoir, permitting a complete circulation of hydraulic fluid duringoperation of the device and permitting the hydraulic system to return toa balanced condition upon removal of pressure from diaphragm 48.

FIG. 3 illustrates a modification of the gearing mechanism whichtransfers the motion of lever arm 30 to indicator needle 10. Thus, agear train comprised of idler gear 66, transfer gear 68 and secondarygear 70 is interposed between rack 28 and gear wheel 26 to providemultiplication of the motion of needle arm 10 with respect to the motionof lever arm 30, as is well known in the gear train art. Thisamplification permits a larger scale to be used on the indicator face tomake the reading of pressure values easier. Thus, indicator face 12 isshown as including two calibrated scales at 16, the one scale being usedwith one gear arrangement and the other scale being used with themultiplier gear arrangement.

In operation, the indicator device is fixed by means of arm band 18 insuch a position that the flexible diaphragm 48 is in contact with anartery or vein so as to detect the pulsations thereof. The arm band istightened to the point where the diaphragm is able to sense motion inthe artery 52. Normally, this will involve a tightening of the banduntil indicator needle 10 indicates a redetermined point on the scale16, thus insuring that the diaphragm will be pressed against the arterywith the same amount of force during each usage of the device.Tightening of the arm band forces a certain amount of fluid out ofreservoir 46, through valve chamber 60 and feed line 40 into thehydraulic assembly 34 to cause the indicator needle to rotate to thedesired point. Pulsations in artery 52 cause further changes in thevolume of the reservoir 46, forcing additional hydraulic fluid throughvalve opening 54, through chamber 60 and feed line 40 into the fluidchamber of ram assembly 34, causing the fluid chamber to expand andforcing piston 36 out of housing 38. As long as the pressure inreservoir 46 due to the expansion of artery 52 is greater than thepressure in chamber 60, fluid will continue to flow through opening 54to increase the pressure in assembly 34. Since the bleeder tube 42 has avery small orifice at 44, there will be a relatively insignificant flowof hydraulic fluid from the fluid chamber of cylinder 34 back toreservoir 46. When the pressure on each side of valve opening 54 isequalized, further pulsations of artery 52 will not force open valveclapper 62 and the pressure in assembly 34 will stabilize. Of course,there will be a small amount of flow back to reservoir 46, but this willbe sufliciently slow to permit the pulsations of the arteries to supplyadditional fluid through valve opening 54 to maintain the pressure inthe fluid chamber of cylinder 34 at a substantially constant value.

The expansion of the fluid chamber in cylinder 34 due to increasedpressure causes piston 36 to move out of housing 38, as has been noted.This motion of piston 36 causes lever arm 30 to rotate counterclockwiseabout its pivot axis 32, which, in turn, causes gear 26 to rotate in aclockwise direction. As the pressure in 34 builds up, indicator needle10 will thus be rotated in a clockwise direction against thecounterclockwise bias of spring 22. When the hydraulic pressure hasreached the maximum value provided by the pulsations in artery 52, theindicator needle will be at a location proportional to and indicative ofthat pressure. By proper adjustment of the tension of hair spring 22 andby proper calibration of the scale, a direct reading of the bloodpressure in artery 52 may then be obtained. By reason of the one-wayvalve arrangement and the small orifice in the bleeder tube, there willbe no appreciable fluctuation in the needle indication.

It will be apparent that the present device can be used to measuresystolic and diastolic blood-pressures in the manner of well knownsphygmomanometers. For this use, of course, a stethoscope or the likewill be required to detect the absence and the presence of a pulse asthe pressure applied on the artery by diaphragm 48 is increased anddecreased. However, the present device is not specifically designed forthat type of use, but rather is designed to provide a continuousmonitoring of the blood-pressure at a value between the systolic anddiastolic values.

Thus, the primary use of the present device will be in providing acontinuous monitoring of a patient where it is particularly desirable towatch closely for and to measure changes in blood pressure. Although thedevice as above described is designed to provide a substantially stableindication of blood pressure, it may in some circumstances be desirableto permit a fluctuation of needle to provide an indication of pulserate. This may be accomplished by making orifice valve 44 larger so asto permit a faster drain of the fluid chamber in hydraulic assembly 34.This will permit the pressure to fall off between each pulse in artery52 and will result in corresponding movement of indicator needle 10 byspring 22. Since the needle will fall back toward its rest position at asubstantially constant rate, the distance that it falls back betweensucceeding pulses will be a rough measure of the pulse rate. Thus, thefaster the pulse rate, the shorter the distance the needle will fallback toward its rest position between pulses. Similarly, the slower thepulse rate the longer will be the periods between succeeding pulses andthe further the needle will fall toward rest position. By carefulcalibration of the indicator scale and by careful adjustment of the sizeof orifice valve 44, it will be possible to obtain a rough directreading of pulse rate by watching the point on the calibrated scale towhich needle 10 falls back during the pauses between pulses. Thisreading, of course, will only be an indication of pulse rate, and willbe dependent on blood pressure for accuracy, but will be adequate topermit quick checks on a patients condition. Further, this type ofindication is highly useful in detecting changes in condition.

Referring now to FIG. 4, there is illustrated a modification of, oraccessory to, the present invention which permits transmission of bloodpressure and pulse rate readings to a remote location. The illustratedsystem provides for the transmission of these signals over conventionaltelephone lines; however, it will be apparent that the system can beadapted to other types of transmission systems. In order to permit thetransmission of pressure and pulse readings, it is necessary to convertthe measured values into electric signals. This may be accomplishedthrough the use of a stress-sensing device of known type, such as acarbon pile resistor, which changes its value of resistance withchanging pressure. Such a stress sensor, indicated at 72 in FIG. 4, maybe adapted to respond to the hydraulic assembly 34 to sense thepulsations. Other arrangements will be apparent to those skilled in theart. As illustrated in FIG. 4, the carbon resistor sensor 72 isconnected in series with a small Voltage battery cell 74, the seriesarrangement being connected across a suitable meter 76. Meter 76 servesto indicate the variations in resistance of sensor 72 to provide anindication of the changes in resistance of sensor 72. These changes inresistance, as noted above, will be proportional to the pressure builtup in the hydraulic system and thus will provide an indication of bloodpressure. If the hydraulic system is arranged to provide a varyingpressure, the meter will, of course, reflect these variations and thuswill provide an indication of pulse rate. Also connected across theseries arrangement of the sensor 72 and cell 74 is an amplifier andencoder 78 which amplifies the signals representing the resistance ofsensor 72 and changes them to a form which is suitable for transmissionto a remote location. The output of amplifier and encoder 78 may beapplied to a conventional telephone line 80 by any suitable known means,for example, by dialing a code number on a conventional telephone. Thesignals thus applied to the transmission line are transferred to acentral telephone exchange 82. The telephone exchange may respond to theencoded signals themselves or to the code number dialed first by theuser of the system to connect the signals to a telephone companycomputer '84. The computer deciphers the coded number and completes thecall through a doctors ofiice or hospital switchboard 86 for automaticconnection to a decoder and chart recorder 88. The chart recorder willthen respond to the input signals to produce a trace corresponding tothe variations in resistance of sensor 72. The chart record may then beread by a doctor or technician to determine the pulse and blood pressureof the patient. It will be apparent, of course, that the telephone linemay be omitted from this system and that the amplifier and decoder maybe connected through a suitable transmission line directly to acorresponding decoder and chart recorder at a central point. Such anarrangement will permit a single technician to monitor a plurality ofpatients at one time from one location.

Thus there has been described a simple, lightweight and portableapparatus for measuring and monitoring blood pressure or pulse rate of apatient. It will be apparent to those skilled in the art that manyvariations and modifications of the basic concept can be devised;therefore, it is desired that the foregoing illustration be taken asillustrative and that the scope and extent of the invention be limitedonly by the following claims.

We claim:

1. A. compact, portable transducer for continuous monitoring of theblood pressure of a patient, comprising hydraulic means including afluid reservoir having a flexible wall, an expansible chamber assembly,and transfer means for carrying fluid from said reservoir to saidexpansible chamber assembly upon compression of said reservoir, saidtransfer means including means for retarding the return of said fluid tosaid reservoir; indicator means responsive to the expansion of saidassembly; and means for positioning said flexible wall for response tocirculatory system pulsations in said patient, said pulsations exertingpressure on said flexible wall to cause fluid in said reservoir to flowinto and to expand said expansible chamber assembly in proportion to thepressure on said flexible wall, whereby said indicator means provides acontinuous indication of the fluid pressure in said expansible chamberassembly and thus of the blood pressure of said patient.

2. The mechanism of claim 1, wherein said indicator means comprises ameter having a calibrated scale and a needle connected to saidexpansible chamber assembly, whereby direct readings of blood pressurecan be obtained.

3. The mechanism of claim 2, further including a housing for saidhydraulic means and said indicator means, said flexible wall of saidreservoir forming a portion of said housing.

4. The mechanism of claim 1, wherein said transfer means for carryingsaid fluid to said reservoir includes one-way valve means interposedbetween said reservoir and said expansible chamber assembly to permitfluid flow to said expansible chamber assembly upon compres sion of saidreservoir.

5. The mechanism of claim 4, wherein said means for retarding the returnof said fluid includes bleeder means for returning fluid from saidexpansible chamber assembly to said reservoir, whereby fluid pressurebuilt up in said expansible chamber assembly is released gradually uponrelease of pressure on said flexible wall.

6. The mechanism of claim 5, wherein said indicator means includes ameter having a calibrated scale; means for connecting said meter to saidcxpansible chamber assembly whereby the pressure of fluid in saidexpansible chamber assembly is converted to a corresponding indicationon said meter to provide a direct reading of blood pressure.

7. The mechanism of claim 6, wherein said means for connecting saidmeter to said expansible chamber assembly includes a gear train and alever arm responsive to motion of said expansible chamber assembly todrive said gear train, said gear train being connected to said meter.

8. The mechanism of claim 6, wherein said indicator means furtherincludes sensor means responsive to the expansion of said expansiblechamber assembly for converting the fluid pressure in said expansiblechamber assembly to a corresponding electrical signal, and means fortransmitting said signal to said meter for monitoring of the circulatorysystem of said patient.

9. The mechanism of claim 8, wherein said meter is remote from saidexpansible chamber assembly, whereby said monitoring can be accomplishedat a location remote from said patient.

10. The mechanism of claim 5, wherein said bleeder means includes anorifice value sufliciently small to permit the fluid presser in saidexpansible chamber assembly to build up to a value proportional to thepressure exerted by said circulatory system pulsations and to remain ata substantially constant value between said pulsation whereby saidindicator means provides a constant reading of blood pressure.

11. The mechanism of claim 5, wherein said bleeder means includes anorifice valve sufliciently small to permit the fluid pressure in saidexpansible chamber assembly to build up to a value proportional to thepressure exerted by said circulatory system pulsations, and large enoughto permit a portion of said fluid pressure to bleed between saidpulsations, whereby said indicator means fluctuates to provide readingsof both blood pressure and the rate of said pulsations.

12. The mechanism of claim 5, wherein said bleeder means comprises anorifice valve having an opening substantially smaller than the openingof said one-way valve means.

13. The mechanism of claim 12, wherein said expansible chamber assemblyincludes a fluid chamber and a movable piston, said fluid chamberreceiving fluid under pressure from said reservoir and said pistonmoving in response to the pressure of said fluid.

14. The mechanism of claim 13, wherein said indicator means includes ameter having an indicator needle; means for connecting said needle tosaid piston whereby the pressure of fluid in said fluid chamber isconverted to a mechanical motion of said needle, and spring means urgingsaid needle in a direction to oppose movement of said piston when saidfluid pressure increases.

15. The mechanism of claim 14, wherein said means for positioning saidflexible wall for response to circulatory system pulsations comprises ahousing for said hydraulic means and said indicator means, said flexiblewall of said reservoir forming a portion of one wall of said housing,said meter being mounted on another wall of said housing, and means forholding said flexible wall in contact with the skin of the patient.

References Cited 3 0 UNITED STATES PATENTS Buchmann, German applicationNo. 1,006,581, Apr. 18, 1957.

WILLIAM E. KAMM, Primary Examiner

